OBELIX is an experiment designed to study exclusive final states of antiproton and antineutron annihilations at low energies, with protons and nuclei.
The physics motivations are:
A rather established consensus in the theoretical/phenomenological activity concerns the prediction of the mass region which should be populated by gluonium and hybrids states.
These mesonic resonances are expected in the low mass region of the hadron spectrum (between 1.0 and 2.5 GeV/c^2). Since this region is overpopulate by the standard q qbar mesons and their radial excitations, and a non qbar q object may have allowed qbar q quantum numbers, the task of identifying exotic states is not simple.
The strategy developed in the last few years is to use reactions and processes which can tag the flavor content or the quantum numbers of the produced states and then to compare the production properties of a given new state in different reactions.
OBELIX has focussed its search on the mass region (below 1.8 GeV/c^2), with the am of comparing different type of reactions, specifically with final states containing kaons, taking also advantage of the possibility to change the distribution of the protonium initial states by varying the target densitiy, and, with the nbar beam, to have a pure isospin I=1 in the initial state.
The exploration of the validity of the OZI rule has suggested to OBELIX a systematic study of antinucleon annihilations in the channels omega pi+- and omega pi+-, using both antiproto and antineutron beams. The dramatic OZI violation experimentally observed and the development of the analyses in progress will allows to check the correctness of the hypothesis of the intrinsic strangeness content of the nucleon.